Design of a 3 T REBCO Dipole Magnet Considering Screening Current Induced Magnetic Field and its First Test Result at 77 K

REBa
${_{2}}$
Cu
${_{3}}$
O
$_{7-\delta }$
(REBCO) coated conductor is a promising material for future accelerator magnets. The flat and wide geometry of REBCO tapes can result in the screening current induced magnetic field (SCF), leading to a significant influence on magnetic field quality in REBCO magnets. Considering the influence of the SCF on field quality, we designed a block-type dipole magnet consisting of six no-insulated double-pancake coils wound with REBCO tapes, capable of theoretically achieving 3 T at 4.2 K. We optimized the position of each coil and applied passive and active shimming structures to improve the field quality during the magnet design. According to numerical simulations, the absolute value of sextupole coefficient
${b_{3}}$
could be increased from 0.0681 units to 33.2 units by the SCF. To address this issue, passive and active shimming structures were specifically designed for the
${B_{3}}$
field. As a result, the absolute value of
${b_{3}}$
in the 20 mm aperture could be reduced from the original 33.2 units to 0.881 units and 0.322 units, respectively. The magnet was constructed and tested at 77 K. The central magnetic field reached 0.59 T as expected when the magnet was charged to 38.9 A. The no-insulation characteristics of the magnet based on the test results were discussed.